Gas-operated gas-blast circulating-type circuit breaker with simplified pneumatic control



Jan. 16, 1968 J. M. TELFORD 3,364,325

GAS-OPERATED GAS-BLAST CIRCULATING-TYPE CIRCUIT BREAKER WITH SIMPLIFIEDPNEUMATIC CONTROL 2 Sheets-Sheet l Filed'Dec. 7, 1964 4 INSULATIONINSULATION 3 CLOSE msuumow P' Jan. 16 1968 TELFORD 3,364,325

GAS-OPERATED GAS-BLAST CIRCULATING-TYPE CIRCUIT BREAKER WITH SIMPLIFIEDPNEUMATIC CONTROL Filed Dec. 7, 1964 2 Sheets-Sheet 2 HIGH PRESSURE GASPRESSURE SWITCH PUMP LOW PRESSURE GAS INVENTOR James M.Te|ford M/QMATTORNEY United States Patent O GAS-OPERATED GAS-BLAST CIRCULATING-TYPECIRCUIT BREAKER WITH SIMPLIFIED PNEU- MATIC CONTROL James M. Telford,Pittsburgh, Pa., assiguor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 7, 1964, Ser.No. 416,262 4 Claims. (Cl. 200-148) ABSTRACT OF THE DISCLOSURE Acompressed-gas circulating-type circuit interrupter of the pressurizedtank type has a pair of arcing contacts and a pair of serially-relateddisconnecting contacts disposed Within a metallic dead tank having apair of terminal bushings extending therein. One terminal bushingsupports a stationary disconnecting contact structure, and the otherterminal bushing is electrically connected through an interruptingassembly to the movable isolating contact. A highly efiicient gas, suchas sulfur hexafluoride (SP is used; and an exhausting blast tube extendsfrom the interrupting assembly into a low-pressure externally-disposedtank. A simplified pneumatic control scheme is used involving a minimumnumber of valves for efficient sequential operation of the arcing anddisconnecting contacts. A three-way air-pilot-operated normallyclosedfirst valve has a tank connection to the closing side of the piston forthe disconnecting contact under deenergized conditions. A two-Waynormally-closed second valve disposed externally of the pressurized tankcontrols the pilot section of the first valve through acheck-valve-controlled pneumatic line. A three-way normally-open tripvalve controls the exhausting or pressurizing of the cylinders for thearcing contacts; and an auxiliary switch has a direct pneumaticconnection to the pilot section of the first valve.

This invention relates, generally, to circuit breakers and, moreparticularly, to gas-blast circuit breakers of the dual-pressure type.

Prior gas-blast circuit breakers have required either costly mechanismsfor mechanically operating the breakers or complicated valves forcontrolling fluid-pressure actuated operating means. Furthermore, inbreakers utilizing compressed air as the arc-extinguishing medium theair is exhausted to atmosphere after passing through the circuitinterrupters in a circuit breaker. This is not economical when anexpensive interrupting gas is utilized as the arc-extinguishing medium,

An object of this invention is to provide a circuit breaker in which aninterrupting gas stored in a h gh pressure tank is utilized as anoperating medium, thereby eliminating a costly mechanism, mechanicallinks and shaft seals from the breaker structure.

Another object of the invention is to provide a gasblast circuit breakerof the dual-pressure type in which the arced interrupting gas is blastedinto a low pressure chamber and then filtered before being returned tothe high pressure tank, thereby preventing the main parts of theinterrupter and the bushings inside the tank from being exposed to theby-products of the arced interrupting gas.

3,364,325" Patented Jan. 16, 1968 A further object of the invention isto provide for utilizing standard commercially available valves forcontrolling the operation of the contact members of the interrupters andthe isolating switch of a gas-operated gasblast circuit breaker.

Other objects of the invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a circuit breakercomprises a relatively high pressure tank and a relatively low pressurechamber which are connected in a closed system. An interrupting unit andan isolating switch mounted inside the tank on the lower ends ofterminal bushings establish a series circuit through terminal conductorsinside the bushings. The contact members of the interrupter and theisolator are operated by the high pressure gas in the tank andcontrolled by standard, commercially available valves. When theinterrupter is opened, the high pressure gas is blasted through the arc,into an orifice and out through a blast tube into the low pressurechamber. After the interrupter has reached its open position, theisolator is opened and the interrupter is then reclosed. When the interrupter opens and high pressure gas is blasted into the low pressurechamber, the change in differential pressure starts a pump and the arcedgas is returned to the high pressure tank through a filter.

For a better understanding of the nature and objects of the invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawing, in which FIGURES 1A and 1Bconstitute a diagrammatic view of a circuit breaker and controlapparatus embodying principal features of the invention, the contactmembers of the breaker being in the closed position.

Referring to the drawing, the circuit breaker 1 shown therein may be ofa three-phase type having three pole units, only one of which is shownin the present drawing. Preferably, each pole unit comprises a generallycylindrical high pressure tank 2, which is supported by feet 3, and alow pressure reservoir 4 attached directly to the tank 2. The tank 2 isgrounded for safety reasons.

An interrupting gas, for example, sulfur hexafiuoride, SP gas, isretained in the tank 2 under four or more atmospheres pressure. The gasin the low pressure reservoir 4 is held at one atmosphere pressure.Other interrupting gases, such as selenium hexafluoride, SeF may beutilized if desired.

Terminal bushings 5 are mounted on top of the tank 2. Each terminalbushing contains a conductor (not shown) which carries current into thepressurized tank 2 to be interrupted by an arc-extinguishing assemblage6. The assemblage 6 is mounted on a metal base 7 attached to aconducting supporting plate 8 by insulating mem bers 9. The plate 8 isattached to the lower end of one terminal bushing 5. A stationarycontact member 10 is attached to the lower end of the other terminalbushing 5. The arc-extinguishing assemblage 6 may be of the typedescribed in a copending application Serial No. 59,882, filed October 3,1960, now US. Patent 3,214,540, issued October 26, 1965, and assigned tothe Westinghouse Electric Corporation.

As shown, each arc-extinguishing assembly 6 includes a separable pair ofmain contacts 11, a pair of main interrupting contacts 12, and a pair ofresistance or impedance interrupting contacts 13. The main interruptingcontacts 12 and the resistance interrupting contacts 13 exhaust into aninsulating blast tube 14 which is connected directly to the low pressurechamber 4. A resistance or impedance 15 is connected in series with theresistance contacts 13 and serves to facilitate the interruption of thecurrent through the main interrupting contacts 12. As well known in theart, the insertion of the impedance 15 into the circuit during a portionof the interrupting operation reduces the magnitude of the current to beinterrupted.

The interruption of the resistance current by the resistance interrupter13 completely interrupts the passage of current through thearc-extinguishing assembly 6. After the interruption of the current, itis desirable to disengage a movable isolating contact member 16 from thestationary contact member 10. By providing an isolating gap 17 betweenthe isolating contacts, which maintains the circuit open, reclosure ofthe main contacts 11, the main interrupting contacts 12 and theresistance contacts 13 may then be efifected. Since the interior region18 of the tank 2 contains gas at a relatively high pressure, it isobvious that the disconnecting gap is in a high dielectric strengthatmosphere and, consequently, only a relatively small disconnecting gapdistance need be provided. Therefore, the circuit breaker may bereclosed in a relatively short time.

During an interrupting operation the main contacts 11 are separatedfirst, then the main interrupting contacts 12 are separated, and thenthe resistance contacts 13 are separated. After the separation of theresistance contacts the isolating contact 16 is separated from thestationary contact 10, after which the contacts 11, 12 and 13 arereclosed. The circuit is maintained open by the separated disconnectingor isolating contact 16. Thus, the circuit breaker may be reclosed bymerely efi'ecting re-engagement of the isolating contact 16 with thecontact 10.

The structure and manner of operation of the arcextinguishing assembly 6is fully described in the aforesaid copending application. Accordingly,only a general description is given herein. Referring to the drawing, itwill be seen that the arc-extinguishing gas for interrupting currentflow between a relatively stationary orifice contact 19 and a movablemain arcing contact 20 of the main interrupting contacts 12 is exhaustedoperatively through a cup-shaped contact support 21 and into theinterior 22 of the low pressure chamber 4 through the blast tube 14. Tofacilitate centering of the main current are drawn through the orificecontact 19, and the receiving of a radial inward blast of gas, an arccentering horn 23 is provided. The are horn 23 is perforated and ispositioned by a supporting arm 24 which is fastened by bolts 25 to ashoulder portion of the contact support 21. An opening 26 in the base 7registers with the opening through the contact support 21 and, aspreviously mentioned, the blast tube 14, which is attached to the base 7around the opening 26, communicates with the interior of the lowpressure reservoir 4.

Similarly, a relatively stationary orifice contact 27 and a relativelymovable resistance contact 28 are separated to draw a resistance currentarc, which is subjected to a gas blast from the region 18 interiorly ofthe tank 2, through the orifice opening 27 and out through an opening 29and the blast tube 14 to the region 22 within the low pressure chamber4.

As shown in the drawing, the main current contacts 11 include aplurality of inwardly extending contact fingers 31 which engage amovable main contact member 32. The contact fingers 31 are attached tothe metal base 7. The movable contact member 32 is biased downwardly bycompression springs 33. The movable contact member 32 is attached bymeans of a piston rod 34 and a spacing sleeve 35 to a piston 36 operatedvertically within an operating cylinder 37. As will be described morefully hereinafter, exhausting of the gas pressure above the piston 36will effect upward opening movement of the piston 36 and the movablecontact member 32. This will force the current passing through the maincontacts 11 to flow by means of the main interrupting contacts 12 andthe resistance interrupting contacts 13, although the latter will carrya relatively small proportion of the current be cause of the presence ofthe series resistance The main movable arcing contact member 20 isrnoved upwardly by a piston 38 movable within an operating cyl= inder 39and biased downwardly in a closing direction by a compression spring 49.The upper end of anupwardly extending portion 41 of the contact member20 which is secured to the piston 38 has a reduced spindle valve ertion42 and an upper enlarged valve spool portion 43. As a result, the valveportions 42 and 43 form a sleeve valve which prevents or permitscommunication between a passageway 44 and a passageway 45 leading to theregion above a piston 46 of the impedance interrupting unit 13. Thepassageway 45 is connected to a passageway 47 in a cylinder head 48 ofthe interrupter 13 by means of an insulated tube 49.

The movable contact member 23 of the resistance interrupter 13 iscarried by the piston 46 which operates in a cylinder 51. The piston 46is biased downwardly by a compression spring 52 disposed between apiston head 53 and the cylinder head or body 48. When gas is exhaustedfrom above the piston 46 the pressure of the gas Within the tank 2 onthe piston head 53 forces the piston 46 up wardly against thecompression of the spring 52.

The isolating or disconnecting switch structure, which is designatedgenerally by the reference numeral 55, ineludes the disconnectingcontact member 16 which is actu= ated by pressure differences across apiston 56 movable within an operating cylinder 57. Relatively stationarycontact fingers 58 bear upon the sides of the movable disconnectingcontact 16 to transmit current therethrough from a cylinder head 59. Thecylinder head 59 is electri cally and mechanically connected to the base7 by a conducting and supporting member 60. The resistor 15 is connectedto the support plate 8 by a conductor 64. The plate 8 is connected tothe main interrupter unit 12 by means of a conductor 65.

In the closed circuit position of the breaker as shown in V the drawing,the current path extends through the terminal conductor enclosed by oneof the terminal bushings 5, the support plate 8, the conductor 65 andthrough the closed contacts 11, 12 and 13 to the conducting base 7. Thecurrent path then extends through the conducting member 60, thedisconnecting contact structure 55 and the contact member 16 whichengages the contact mem ber 10, and thence to the terminal conductor inthe other bushing 5.

The operation of the circuit breaker is controlled by a solenoidoperated, three way, normally open trip valve 71, a solenoid operated,straight way normally closed close valve 72 and a gas-pilot operated,three Way, nor= mally closed valve A with an internal bleederconnection, indicated by the dotted line a, between the pilot sectionand outlet. The valves 71, 72 and A are standard com mercially availableair or gas valves. The trip valve 71 is of adequate capacity to exhaustthe interrupters at the desired rate. As an alternative, two or moresmaller valves may be used in parallel for tripping by connecting theoperating coils in series or parallel. Valves B and C are standard,commercially available check valves. One each of valves A, B and C isrequired for each interrupter. One each of the close and trip valves isrequired per circuit breaker, or multiple trip valves may be paralleledas indicated above.

An auxiliary switch 73 is operated by a double acting fluid-pressurecylinder 74, the front or stem end of which is connected to the highpressure tank 2 through a pipe 75. Pressurizing or exhausting the rearend operates the piston inside the cylinder due to the piston areadifierential. A sensing, or indicating, line 76 from the rear of thecylinder 74 may be connected to the pilot of the isolator control valveA as shown, or directly to the rear of the isolator cylinder 57. Ineither case the indicating line 76 will indicate the pressure conditioncontrolling the position of the isolator contact 16.

A pressure switch 77, connected to the low pressure reservoir 4 controlsthe operation of a pump or compressor 78. The switch 77 may be of a typewell known in the art. When the breaker opens and high pressure gas isblasted into the low pressure reservoir 4, the change in pressure willoperate the switch 77 to start the pump which draws gas from thereservoir 4 through a filter 79 and returns it to the high pressure tank2, thereby restoring the original differential in pressure between thetank and the reservoir.

In the drawing, the circuit breaker is shown in the closed position.Energizing the solenoid 81 of the trip valve 71 by means of anyconventional electrical control scheme through a conductor 82 andcontact members 83 of the auxiliary switch 73 closes the valve 71 andexhausts tube 84 leading to the interrupters. This exhausts the highpressure gas from the top of the interrupter pistons into the lowpressure chamber 4 through a pipe 85, causing the main contacts 11, themain interrupting contacts 12 and the resistor interrupting contacts 13to open in sequence and interrupt the current through the circuitbreaker. When the main and the resistor interrupters open, the highpressure gas is blasted through the blast tube 14 into the low pressurereservoir 4. As described in the aforesaid copending application, thesequential operation of the interrupters is obtained by means of sleevevalves 86, 87, and 88 in the interrupters 11, 12 and 13, respectively.

Opening the resistor interrupter 13 permits the pilot section 89 ofvalve A to be exhausted through check valve C and a line 80. Valve Awill thus move to its normally closed position, exhausting the isolatorcylinder 57 through lines 9t} and 91 into the blast tube 14 and causingthe isolator contacts 16 to move to the open position. At this time thesensing line 76 is also exhausted, causing the auxiliary switch 73 toopen contacts 83 and close contacts 93. Opening contacts 83 deenergizesthe solenoid 81, permitting the trip valve 71 to return to its normallyopen position. This admits high pressure gas from the tank 2 to the topof the interrupter pistons to reclose the interrupter contacts and theblast orifices. Reclosing the resistor interrupter readmits pressure inthe line 80 leading to check valve C. However, the check valve preventsgas flow to the pilot section of valve A. The isolator cylinder thusremains exhausted, maintaining the breaker open position.

Since the tubes from the pilots of valves A for other interrupting unitsof the breaker all have a common connection at the close valve 72, checkvalves B are provided to prevent the exhausting of the pilots of allvalves A by the first interrupter to open. This interlocks each isolatorwith its own interrupter.

The closing operation of the circuit breaker is initiated by energizingthe solenoid 94 of the close valve 72 through a closing circuit and thecontacts 93 of the auxiliary switch 73. This opens the valve 72admitting pressure from the tank 2 through check valve B to the pilotsection 89 of valve A and causing it to move to the open position. Highpressure gas is admitted from the tank 2 through an inlet opening 95 inthe valve A to the isolator cylinder 57, thereby actuating the piston 56to cause contact member 16 to engage contact member and close thecircuit through the breaker since the interrupters have been recloscdpreviously. The front of the isolator cylinder is connected to the lowpressure chamber at all times through lines 96, 91 and the blast tube14.

At this time, the auxiliary switch 73 is operated to open contacts 93and close contacts 83, thereby deenergizing the solenoid 94 whichpermits the valve 72 to move to its normally closed position. Trappedgas pressure in the pilot section of valve A, maintained by the bleederconnection, holds valve A in the open position, thus maintaining 6 theisolator contacts in the breaker closed position until another trippingoperation is initiated.

As previously explained, the circuit breaker may be either a single poleor a multiple pole breaker, each pole unit being similar to the oneherein shown and described. Also, a simplified interrupting structuremay be utilized in which the main contacts and the resistor interrupterare omitted, only the main interrupter and the isolator being providedfor each pole unit.

From the foregoing description, it is apparent that the inventionprovides a circuit breaker in which an interrupting gas stored in thebreaker under pressure is utilized as an operating medium for operatingthe contact members of the breaker, thereby eliminating a costlymechanism, mechanical links and shaft seals required in prior gasblastcircuit breakers.

Also, the arced gas is blasted out through a blast tube into a lowpressure chamber and then filtered before being returned to the highpressure tank. Thus, the main parts of the interrupter and the bushingsinside the tank are not exposed to the by-products of the arcedinterrupting gas.

Furthermore, the operation of the breaker is controlled by a smallnumber of standard commercially available valves. The simplicity of thecontrol scheme, with the resulting low cost and maintenance, is animportant advantage.

Certain features of the pneumatic control scheme are set forth andclaimed in US. patent application Serial No. 416,455, filed Dec. 7,1964, by William A. Fish, Jr., and James M. Telford, and assigned to theassignee of the present application.

Since numerous changes may be made in the abovedescribed construction,and different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all the mattercontained in the foregoing description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim as my invention:

1. A compressed-gas circuit interrupter of the closed circulating typeincluding means defining a pressurized tank containing a highlyefficient arc-extinguishing gas under pressure, an interrupting assemblywith an exhaust structure and a serially related disconnecting contactstructure disposed within said tank including a pair of separable arcingcontacts (27, 28) and a pair of seriallyrelated disconnecting switchcontacts (10, 16) all disposed within said pressurized tank, alow-pressure tank disposed externally of the aforesaid tank andconnected to said exhaust structure, an isolator piston (56) for movingone of said disconnecting switch contacts to the open and closed-circuitpositions, a three-way normally-closed first control valve (A) having agas-operated pilot section (89) for pressurizing or exhausting theclosing side of said isolator piston (56) and disposed within thepressurized tank adjacent the disconnecting switch contacts, anoperating piston (46) movable within a cylinder for opening one of saidarcing contacts, a main exhaust second valve (71) for pressurizing orexhausting the closing side of said operating piston (46), acheck-valve-controlled pneumatic line pneumatically interconnecting theclosing side of said operating piston (46) with the pilot section (89)of said first control valve (A), and a check-valve-controlled pneumaticline pneumatically interconnecting the pilot section (89) with a two-waynormally-closed third close valve (72) to pressurize the pilot section(89) and thereby open the first control valve (A) to close the isolatorpiston (56).

2. The combination according to claim 1, wherein a main contactstructure (11) and a main arcing contact structure (12) is in electricalparallel with said pair of separable arcing contacts.

3. The combination of claim 2, wherein a resistance is disposed seriallyin circuit with the last mentioned pair of separable arcing contacts(27, 28).

4. The combination according to claim 1, wherein a pressure switchcontrols a pump to raise the pressure of gas from the low-pressure tankto the level requisite for feeding into the pressurized tank.

References Cited UNITED STATES PATENTS 2,459,600 1./ 1.949 .Strom 2001488 10/1960 Caswell et al. 200-148 11/1961 Schrameck et al 200148 10/1965Schrarneck et a1. 200-145 FOREIGN PATENTS 3/ 1960 France. 11/ 1946 GreatBritain.

ROBERT S. MACON, Primary Examiner.

